Wait. What do you think "evil" means? What do you think character development is?
that they would rather cut MC throat than be kinder.
Yeah, um, that would be smart
Now, I would like to imagine that they're "evil" for reasons above and beyond being evil for the sake of being evil.
I don't understand how this article is related to what I said. In your understanding, evil characters should always become pitiful and kind, redeeming, in order to become stronger (develop)? To me, it doesn't, and that doesn't make them stupid.
For changes, the character doesn't have to become kinder or redeem something.. Otherwise, every good character would have to experience the "fall arch", but WOW, for some reason, this does not happen. They remain the same kind and no one says that they do not have growth. Or in your understanding ,the "evil" character is always "stupid" because he is evil? Also strange.
Some of them will always be cruel, cold, too selfish, and so on, maybe this is the basis of their personality. And chaotic characters don't even need a good reason to hurt others. Neutral evil can always pursue its own benefit, it never ends. Why do they have to suddenly reconsider their views? Lifestyle? Idk. Instead, they can develop in this direction. Was a thief? Become the king of thieves! Stronger. More domineering. More merciless. And so on.
I wrote about "throat" because I want the evil characters to have clear views. Just as clear as the good characters who leave your squad because you do too many evil things. You know what I mean? It is better to let them betray MC for the sake of their views than to be another victim of the "arch of redemption".